Tornado Hunters May Have an Unlikely New Ally: Electricity.
While tornadoes have been portrayed as large fluid-like vortexes, tornado prediction has been spotty because we neither understand why they sometimes form and sometimes don't nor how to tell for sure one is forming until it's almost on the ground. New insight may eventually change that.
Armed with only an antenna mounted on top of a vehicle and a simple receiver, researchers have been able to pick up low-frequency electromagnetic waves – a possible sign that a tornado is brewing. The frequency of the signal should even be able to tell them the ferocity of the storm.
There is a theory about how the electric fields of tornadoes evolve.
When dust particles picked up by the storm and droplets rub against each other, they become oppositely charged. The lighter particles, which are mostly negative, get blown to the top of the funnel, while the heavier positive ones sink to the bottom, they say.
In theory this "charge separation" is what may cause an electric field to form, a voltage difference between the positively charged and negatively charged clouds of particulates and water droplets. The theory continues:
As the separated particles rotate around the vortex, they act as a source of low frequency electromagnetic radiation. Non-rotating storms produce nothing more than electrical noise.
One wonders, however, whether their explanation goes far enough in implicating electromagnetic goings on. The theory seems to go on the assumption that charges are naturally completely neutral and must somehow be "separated" before anything electrical can happen.
What if, on the other hand, charges came pre-separated and the weather we see (lightning and tornadoes primarily) is generated as a method of neutralizing existing separated charges through short-lived currents (large-scale electrostatic discharges)?
There have been a number of papers in recent (and not-so-recent) years attempting to connect the dots between observed electrical signatures, such as the EM radiation noted in the New Scientist article, with tornadogenesis.
One experiment, performed by Bernard Vonnegut, involved the investigation of electrical discharges under experimental conditions.
Without a vortex, a stable spark could not be maintained if the electrodes were more than 37 mm apart. A spark between electrodes having the separation is shown in fig. 3. When the blower was turned on and a vortex was created, we observed that the discharge between the electrodes became more steady, that its diameter increased, and that it appeared to assume the characteristic of a glow rather than a spark discharge. Fig. 4 shows the appearance of the discharge when the vortex is present. When the vortex was turned on, we observed that the potential difference across the discharge dropped from 6.0 kv to 4.3 kv and that the current increased from 17.5 to 19 milliamperes. It was also observed that, without the vortex, the discharge produced considerable radio-frequency noise in the broadcast band but that, when the vortex was turned on, this noise disappeared.
It was further observed that with the vortex it was possible to obtain a stable discharge even when the electrodes were as much as 68 mm apart. Such a discharge is shown in fig. 5. The potential difference in this case is 7.3 kv, and the current is 14.5 milliamperes.
Is it possible that nature acts in much the same way as currents and vortexes in the lab? Could a tornado simply be a less intense electrostatic discharge between the charges in the cloud and the charges in the ground? A glow rather than a spark discharge (such as lightning)?
Such an approach may even illuminate, no pun intended, many anecdotal stories of luminous phenomena associated with the inner structure of tornadoes.
January 21, 1992. Near Cripple Creek, Colorado. Shortly after 2 PM, while fishing at Skagway Reservoir, D. Mc Gown spotted an ominous cloud formation developing in the west. A horizontal, black cloud rolled toward him. Suddenly, it lifted to reveal a huge, twisting funnel advancing directly at him. He threw himself to the ground, but got a good look up into the interior of the funnel.
"The outside of the tornado was spinning so fast my eye couldn't follow it, but the inside was rotating almost lazily. I could see a thousand feet up inside it. Tiny fingers of lightning lined the hollow tube."
Passing over him, the funnel bounced across the lake, ripped up some trees, and was gone.
(McGown, Dennis; "Letters," Time, 147: 8, June 10, 1996)
At 0448 GMT, following a sudden cessation of rainfall, M.D. Smith became aware of an orange glow outside his window. Accompanying it was a roar like that of a military jet. The phenomenon occurred a total of four times; the second of which is the most interesting.
"A second illumination was observed twenty seconds later, but this time it reappeared away from the tree so a clear view was possible. The illumination was in the form of a narrow column and of the classic gentle 'S' tornado shape in the 'roping out' stage; it was silvery in colour towards the top and golden-orange lower down. Additionally, Mr. Smith saw the illumination move from the sky towards the ground, but at a speed slower than lightning. The sound of rushing wind was heard again, while this illumination lasted five to six seconds. Mr. Smith also noted a very low cloud base with a second layer of cloud only slightly higher."
(Reynolds, David J.; "Nocturnal Tornado Illuminated by an Electrical Discharge at Farnham, Surrey, 10 January 1994," Journal of Meteorology, UK, 20:381, 1995.)
May 3, 1943. McKinney, Texas. People rarely get the chance to look up into the funnel of a tornado and live to tell about it. R.S. Hall did; and what he saw is very strange.
"The bottom of the rim was about 20 feet off the ground, and had doubtless a few moments before destroyed our house as it passed. The interior of the funnel was hollow; the rim itself appearing to be not over 10 feet in thickness and, owing possibly to the light within the funnel, appeared perfectly opaque. Its inside was so slick and even that it resembled the interior of a glazed standpipe. The rim had another motion which I was, for a moment, too dazzled to grasp. Presently I did. The whole thing was rotating, shooting past from right to left with incredible velocity.
"I lay back on my left elbow, to afford the baby better protection, and looked up. It is possible that in that upward glance my stricken eyes beheld something few have ever seen before and lived to tell about it. I was looking far up the interior of a great tornado funnel! It extended upward for over a thousand feet, and was swaying gently, and bending slowly toward the southeast. Down at the bottom, judging from the circle in front of me, the funnel was about 150 yards across. Higher up it was larger, and seemed to be partly filled with a bright cloud, which shimmered like a fluorescent light. This brilliant cloud was in the middle of the funnel, not touching the sides, as I recall having seen the walls extending on up outside the cloud.
"Up there, too, where I could observe both the front and back of the funnel, the terrific whirling could be plainly seen. As the upper portion of the huge pipe swayed over, another phenomenon took place. It looked as if the whole column were composed of rings or layers, and when a higher ring moved on toward the southeast, the ring immediately below slipped over to get back under it. This rippling motion continued on down toward the lower tip."
Hall also reported a peculiar bluish light and blue streamers that appeared to consist of vapor. (Hall, Roy S.; "Inside a Texas Tornado," Weatherwise, 40:73, 1987.)
Mr. Will Keller, a farmer of near Greensburg, Kans., is the man to whom reference is made, and the following is substantially his story:
It was on the afternoon of June 22, 1928, between 3 and 4 o'clock. I was out in my field with my family looking over the ruins of our wheat crop which had just been completely destroyed by a hailstorm. I noticed an umbrella-shaped cloud in the west and southwest and from its appearance suspected that there was a tornado in it. The air had that peculiar oppressiveness which nearly always precedes the coming of a tornado.
But my attention being on other matters, I did not watch the approach of the cloud. However, its nearness soon caused me to take another look at it. I saw at once that my suspicions were correct, for hanging from the greenish-black base of the cloud was not just one tornado, but three.
The family had entered the cellar and I was in the doorway just about to enter and close the door when I decided that I would take a last look at the approaching tornado. I have seen a number of these things and have never become panic-stricken when near them. So I did not lose my head now, though the approaching tornado was indeed an impressive sight.
Steadily the tornado came on, the end gradually rising above the ground. I could have stood there only a few seconds, but so impressed was I with what was going on that it seemed a long time. At last the great shaggy end of the funnel hung directly overhead. Everything was as still as death. There was a strong gassy odor and it seemed that I could not breathe. There was a screaming, hissing sound coming directly from the end of the funnel. I looked up and to my astonishment I saw right up into the heart of the tornado. There was a circular opening in the center of the funnel, about 50 or 100 feet in diameter, and extending straight upward for a distance of at least one half mile, as best I could judge under the circumstances. The walls of this opening were of rotating clouds and the whole was made brilliantly visible by constant flashes of lightning which zigzagged from side to side. Had it not been for the lightning I could not have seen the opening, not any distance up into it anyway.
Around the lower rim of the great vortex small tornadoes were constantly forming and breaking away. These looked like tails as they writhed their way around the end of the funnel. It was these that made the hissing noise.
I noticed that the direction of rotation of the great whirl was anticlockwise, but the small twisters rotated both ways -- some one way and some another.
The opening was completely hollow except for something which I could not exactly make out, but suppose that it was a detached wind cloud. This thing was in the center and was moving up and down.
The tornado was not traveling at a great speed. I had plenty of time to get a good view of the whole thing, inside and out.
I am not the first one to lay claims to having seen the inside of a tornado. I remember that in 1915 a tornado passed near Mullinville and a hired man on a farm over which the tornado passed had taken refuge in the barn. As the tornado passed over the barn, the door was blown open and the man saw up into it, and this one like the one I saw, was hollow and lit up by lightning. As the hired man was not well known, no one paid much attention to what he said. [Mr. Keller thought that this tornado was the one shown in photograph opposite p. 448 of MONTHLY WEATHER REVIEW of 1919.]
Mr. Keller is a man apparently between 35 and-40 years of age. His reputation for truthfulness and sobriety is of the best. Apparently he is entirely capable of making careful and reliable observations.
It seems there is a substantial history, on the books, of chance encounters with and observations of the inner structure of tornadoes. These observations, individually, may be only a single anecdote, but together the body of anecdotes may inevitable pass some arbitrary threshold and become evidence to be taken seriously.
Returning to the subject of scientific papers, such notables as Bernard Vonnegut, ER Rathbun, Marx Brook, C Sozou, Bothun, Patton & Sessions, Berson & Power, and Thomas Dehel, et al have all left their technical mark on the hypothesis.
It should be interesting to see how further researches shape up. The recent news article on the probable utility of electrical signals in identifying tornadic activity seems to be indicative that further study of the electrical model may be warranted. It may just give us the information we need to finally nail down how and why tornadoes form, thus improving our predictive ability and the ability to better safeguard lives and property.